1. Field of the Invention
The present invention relates to an image sensor, and particularly to a package process of a backside illumination image sensor.
2. Description of the Related Art
Image sensor has a function of transforming the received optical signals into the electrical signals, and is widely used in various digital image electronic products. A conventional image sensor includes a semiconductor substrate and a sensing component disposed on the semiconductor substrate. Furthermore, the sensing component is covered by a plurality of metallic circuit layers disposed over the semiconductor substrate. The light entering the conventional image sensor must penetrate the metallic circuit layers before arriving at the sensing component. Thus, the light sensitive ability of the sensing component is limited. Recently, in order to improve the light sensitive ability of the image sensor, a backside illumination image sensor is being researched. The backside illumination image sensor includes a sensing component disposed on the rear surface of the semiconductor substrate. A front surface of the semiconductor substrate is only used for disposing a plurality of metallic circuit layers thereon. Because the sensing component of the backside illumination image sensor is not covered by the metallic circuit layers, the sensing component can sense more light. Thus, the light sensitive ability of the image sensor can be improved.
A current package process of the backside illumination image sensor includes the steps of: adhering the semiconductor substrate to a carrier, disposing the sensing component on the semiconductor substrate, forming the metallic circuit layers on the carrier, and so on. Generally, after the semiconductor substrate is adhered to the carrier, the following steps are performed. Thus, the metallic layers formed on the carrier are electrically connected to the semiconductor substrate. First, a plurality of holes corresponding to a plurality of pads on the semiconductor substrate are formed. Then, a metallization process is applied to the holes to form the conductive holes and metallic circuit layers. However, the pads on the semiconductor substrate are invisible after the semiconductor substrate is adhered to the carrier. Thus, it is difficulty to align of the drilling positions of the holes and the pads. As a result, the current package process of the backside illumination image sensor has a low the package efficiency. Furthermore, the inexact alignment of the drilling positions of the holes and the pads will affect the package quality the backside illumination image sensor.
Therefore, what is needed is a package process of a backside illumination image sensor to overcome the above disadvantages.